Ultraviolet disinfection was first used in the United States (the US Environmental Protection Agency completed the first demonstration project of ultraviolet disinfection of sewage in 1970), and it is now widely used in the United States and Canada. Ultraviolet disinfection technology is a kind of physical disinfection method. It has broad-spectrum sterilization ability and no secondary pollution. After more than 30 years of development, it has become a mature, reliable, efficient, and environmentally friendly disinfection technology, and has been widely used in various fields abroad. In my country, due to the limited understanding of its technology, it is not widely used in sewage treatment. However, in recent years, with my country’s increasing emphasis on sewage disinfection and the accumulation of operating experience, ultraviolet disinfection technology will be promoted. It is expected that 80% of the qualified sewage treatment plants will use ultraviolet disinfection in the future, and it will become a replacement for traditional chemical disinfection methods. mainstream technology.
Ultraviolet light is a type of electromagnetic wave. When electrons in atoms transition from a high energy level to a low energy level, they will release excess energy as electromagnetic waves. The stronger the energy of the electromagnetic wave, the higher the frequency and the shorter the wavelength. The wavelength of visible light that the human eye can see is 400nm-700nm. To the naked eye, the electromagnetic wave of 400nm is displayed as blue and purple, and the electromagnetic wave of 780nm is displayed as orange and red. Ultraviolet rays refer to wavelengths shorter than 400nm. Because their spectrum is outside the violet region, it is called ultraviolet (Ultraviolet, UV for short). Ultraviolet light generally refers to electromagnetic waves with a wavelength of 100nm-400nm, which cannot be seen by human eyes.
Ultraviolet rays with wavelengths of 100nm-400nm are divided into UV-A, UV-B, UV-C and V-UV according to their effects and functions on the human body.
UV-A refers to ultraviolet rays with a wavelength of 315nm-400nm. UV-A can make human skin produce melanin and darken the skin.
UV-B refers to ultraviolet rays with a wavelength of 280nm-315nm. UV-B can cause cancer, wrinkle and age the skin.
UV-C refers to ultraviolet rays with a wavelength of 200nm-280nm, of which the ultraviolet rays in the 254nm band have sterilization and disinfection effects. UV-C with a wavelength between 240nm-270nm can directly destroy the DNA and RNA of cells and viruses, making microorganisms quickly die.
V-UV185nm with a wavelength between 100nm-200nm can produce ozone, and ozone in the air or dissolved in water can destroy the cell walls of microorganisms in the form of oxidation, causing the microorganisms to die immediately.
Sterilization principle
All known life forms on earth rely on DNA and RNA as the basis for reproduction and survival.
Both DNA and RNA are composed of four chemical units
Adenine adenine
T-Thymine thymine
C-Cytosine cytosine
G—Guanine
When the cell reproduces, the long chain in the DNA is opened. After opening, the A unit on each long chain will look for the T unit to combine. Each long chain can copy the same chain as the other long chain that has just been separated, and restore the original pre-splitting chain. The complete DNA becomes the basis of new cells. Ultraviolet rays with a wavelength of 240nm to 270nm can break DNA’s ability to produce proteins and replicate. After the DNA and RNA of cells or viruses are damaged, their ability to produce proteins and reproductive capabilities have been lost. Because bacteria and viruses generally have a very short life cycle, bacteria and viruses that cannot reproduce will die quickly.
advantage
1. UV disinfection does not require chemicals and does not produce THMs disinfection by-products;
2. Fast sterilization and good effect;
3. No odor, no noise, does not affect the taste of water;
4. Easy operation, simple management, low operation and maintenance cost.
